Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$209.64	11.436%	$233.6144	$233.61	$233.60	$233.60
Purchase #2	$101.99	11.267%	$113.4812	$113.48	$113.50	$113.50
Purchase #3	$20.32	4.230%	$21.1795	$21.18	$21.20	$21.20
Purchase #4	$135.41	3.809%	$140.5678	$140.57	$140.55	$140.60
Purchase #5	$152.28	10.740%	$168.6349	$168.63	$168.65	$168.60
Purchase #6	$242.99	11.637%	$271.2667	$271.27	$271.25	$271.30
Purchase #7	$54.92	11.201%	$61.0716	$61.07	$61.05	$61.10
7 purchase totals =	$917.55		$1,009.8161	$1,009.81	$1,009.80	$1,009.90